Sudden upper airway obstruction is thought to be a cause of life threatening asphyxia in infants and adults. Spontaneous recovery from obstructive apnea during sleep involves recovery from airway obstruction. The proposed research is designed to investigate the neural regulation of upper airway patency during asphyxia in an animal model (rabbits). The influence of maturation, neural stimulation and environmental factors on aspects of preterminal breaths (asphyxial gasps) will be examined. The activity of various muscle groups gasping will be evaluated.